1. Field of the Invention
The present invention relates to an optical signal multiplexing device that multiplexes optical signals by an optical time-division multiplexing system.
2. Description of the Related Art
In recent years, in an optical fiber communication system, OTDM (Optical Time Division Multiplex) for time-division multiplexing optical signals directly in the state of light is being studied. In multiplexing optical signals, an optical multiplexing device that performs this OTDM multiplexing adjusts phases of the optical signals, by remote controlling transmitting stations that output the optical signals, and OTDM multiplexes the optical signals using the optical signals of which phases are adjusted in advance.
Japanese Patent Application Laid-open No. H7-221708 discloses a technique of compensating for a delay of an optical signal generated by an optical path difference within a node, using dispersion dependency of an optical fiber on a wavelength, when the optical signal passes within each node that constitutes an optical fiber communication system, thereby achieving a precise synchronization of the optical signal concerning the optical fiber communication system.
However, according to the conventional technique described above, because the phases of the optical signals need to be adjusted beforehand by remote-controlling the transmitting stations, there has been a problem in that optical signals of which phases are not adjusted beforehand cannot be OTDM multiplexed.
To progress the use of light in the network, the cost of processing an optical signal directly in the state of light needs to be lower than the cost of converting an optical signal into an electric signal. In other words, in processing light directly in the state of light, when the optical signals cannot be multiplexed simply due to the fact that the phases of the optical signals are not adjusted beforehand, it is considered unlikely that the use of optical signals in the network becomes popular by replacing the electric signals that can be flexibly processed.